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a)
\(5x+60=120\)
\(\Rightarrow5x=120-60\)
\(\Rightarrow5x=60\)
\(\Rightarrow x=60\div5\)
\(\Rightarrow x=12\)
Vậy \(x=12\)
b)
\(213-\left(x+25\right)=112\)
\(\Rightarrow x+25=213-112\)
\(\Rightarrow x+25=101\)
\(\Rightarrow x=101-25\)
\(\Rightarrow x=76\)
Vậy \(x=76\)
c)
\(5^x-25=100\)
\(\Rightarrow5^x=100+25\)
\(\Rightarrow5^x=125\)
\(\Rightarrow5^x=5^3\)
\(\Rightarrow x=3\)
Vậy \(x=3\)
a: Ta có: \(7x+25=144\)
\(\Leftrightarrow7x=119\)
hay x=17
b: Ta có: \(33-12x=9\)
\(\Leftrightarrow12x=24\)
hay x=2
c: Ta có: \(128-3\left(x+4\right)=23\)
\(\Leftrightarrow3\left(x+4\right)=105\)
\(\Leftrightarrow x+4=35\)
hay x=31
d: Ta có: \(71+\left(726-3x\right)\cdot5=2246\)
\(\Leftrightarrow5\left(726-3x\right)=2175\)
\(\Leftrightarrow726-3x=435\)
\(\Leftrightarrow3x=291\)
hay x=97
e: Ta có: \(720:\left[41-\left(2x+5\right)\right]=40\)
\(\Leftrightarrow41-\left(2x+5\right)=18\)
\(\Leftrightarrow2x+5=23\)
\(\Leftrightarrow2x=18\)
hay x=9
(x-14)-20=5
=> x-14 = 25
=> x = 39
Các dạng toán như này lớp 6 ai cũng làm được cả * lười vừa thôi*
Lời giải:
$100=2^2.5^2$
$120=2^3.3.5$
$\Rightarrow ƯCLN(100,120)=2^2.5=20$
a: \(4x^3+12=120\)
=>\(4x^3=108\)
=>\(x^3=27=3^3\)
=>x=3
b: \(\left(x-4\right)^2=64\)
=>\(\left[{}\begin{matrix}x-4=8\\x-4=-8\end{matrix}\right.\Leftrightarrow\left[{}\begin{matrix}x=12\\x=-4\end{matrix}\right.\)
c: (x+1)^3-2=5^2
=>\(\left(x+1\right)^3=25+2=27\)
=>x+1=3
=>x=2
d: 136-(x+5)^2=100
=>(x+5)^2=36
=>\(\left[{}\begin{matrix}x+5=6\\x+5=-6\end{matrix}\right.\Rightarrow\left[{}\begin{matrix}x=1\\x=-11\end{matrix}\right.\)
e: \(4^x=16\)
=>\(4^x=4^2\)
=>x=2
f: \(7^x\cdot3-147=0\)
=>\(3\cdot7^x=147\)
=>\(7^x=49\)
=>x=2
g: \(2^{x+3}-15=17\)
=>\(2^{x+3}=32\)
=>x+3=5
=>x=2
h: \(5^{2x-4}\cdot4=10^2\)
=>\(5^{2x-4}=\dfrac{100}{4}=25\)
=>2x-4=2
=>2x=6
=>x=3
i: (32-4x)(7-x)=0
=>(4x-32)(x-7)=0
=>4(x-8)*(x-7)=0
=>(x-8)(x-7)=0
=>\(\left[{}\begin{matrix}x-8=0\\x-7=0\end{matrix}\right.\)
=>\(\left[{}\begin{matrix}x=8\\x=7\end{matrix}\right.\)
k: (8-x)(10-2x)=0
=>(x-8)(x-5)=0
=>\(\left[{}\begin{matrix}x-8=0\\x-5=0\end{matrix}\right.\Leftrightarrow\left[{}\begin{matrix}x=8\\x=5\end{matrix}\right.\)
m: \(3^x+3^{x+1}=108\)
=>\(3^x+3^x\cdot3=108\)
=>\(4\cdot3^x=108\)
=>\(3^x=27\)
=>x=3
n: \(5^{x+2}+5^{x+1}=750\)
=>\(5^x\cdot25+5^x\cdot5=750\)
=>\(5^x\cdot30=750\)
=>\(5^x=25\)
=>x=2
\(\left(x.7-7\right)\left(x.12+24\right)=0\)
=> \(\orbr{\begin{cases}x.7-7=0\\x.12+24=0\end{cases}}\)
=> \(\orbr{\begin{cases}7x=7\\12x=-24\end{cases}}\)
=> \(\orbr{\begin{cases}x=1\\x=-2\end{cases}}\)
\(170-\left(4+5x\right)=101\)
=> \(4+5x=170-101\)
=> \(4+5x=69\)
=> \(5x=69-4\)
=> \(5x=65\)
=> \(x=65:5=13\)
(x.7-7).(x.12+24)=0
* x.7-7=0 * x.12+24=0
x.7=7 x.12=24
x=7:7 x=24:12
x=1 x=2
vạy x=1 hoặc x=2
170-(4+5x)=101
4+5x=170-101
4+5x=69
5x=69-4
5x=65
x=65:5
x=13
vậy x=13
250:(2x-4)=145-120
250:(2x+4)=25
2x+4=250:25
2x+4=10
2x=10+4
2x=14
x=14:2
x=7
vậy x=7
6.x+3.x-4.x=105
x.(6+3-4)=105
x.(9-4)=105
x.5=105
x=105:5
x=21
vậy x=21
120-20. ( x+4 ) = 100
20. (x + 4)= 120 - 100
20. (x+ 4) = 20
x+4= 20: 20
x+4= 1
x= 1-4
x= -3
vậy x= -3
nhớ k cho mk nha
120-20.(x+4)=100
20.(x+4)=120-100
20.(x+4)=20
x+4=20/20
x+4=1
x=1-4
x=-3
\(5x+\frac{100}{4}=120\\ 5x=120-25\\ 5x=95\\ x=19\)
HT